Harry m



H. M. MGGALL. STEAM ENGINE.

' (No Model.)

Patented May 8, 1894.

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N .'NRNI /1 www d NITED STATES f PATENT ,OEFICE;

HARRY M. MccALL, oF LATRoREQAssicNoE or ELEvEN-TwELETHs To RICHARD c. KENNEDY AND BENJAMIND. REED, oE PITTSRURQ PENN SYLVANIA. K

VsTEM-ENGN E;

SPECIFICATION forming part of Letters Patent No. 519,588, dated May 8, 1 894.

Appiicaion nea August 29,1893. semina-184.280. (No man To all whom it may concern:

Be it known that I, HARRY M. MCCALL, of Latrobe, in the county'of Westmoreland and State of Pennsylvania, have invented certain n ew and useful Improvements in Steam-Engines; and I do hereby declare that the following 1s a full, clear, and exact description of the lnvention, which will enable others skilled 1n the art to which it appertains to make and use the same, reference being had to the accompanying drawings, and to the lettersI of reference marked thereon, which form part of this specification. v i

Thisinvention relates to certain improvements 1n steam engines, and more particularly to improvements in compound or double expansion steam engines. The object of the invention is to provide an lmproved compound double expansion steam engine exceedingly cheap, simple and durable 1n construction, very quick, rapid and sure 1n action, extremely economical in the consumption of steam, and wherein a single cyllnder and piston are employed.

The invention consists in certain novel features 1n construction and in combination of parts more fully described hereinafter and particularly pointed out in the claim.

Referring to the accompanying drawings Figure 1, is a side elevation ofthe improved engine, the steam chest and slide valve being shown in section. Fig. 2, is an enlarged view of the cylinder in horizontal section, the steam chest and slide valve being shown in section, the slide valve being shown in a position it assumes when moving forward and just about to cut off the supply of steam from the rear of 'the cylinder to the front thereof and to open the front of the cylinder to the exhaust. v

a indicates a suitably mounted cylinder.

b indicates the piston inl said cylinder provided with the forwardly extending piston rod d, and the trunk c, extending rearwardly through the rear ofthe cylinder.

c indicates the steam chest, preferably, centrally located on the sidevof the cylinder, and provided-with a steam inlet pipe o, and a suitable valve seat for the slide valve g, operated by the valve rod f, by any suitable connections. This valvev seat is lprovided with three parallel ports' k, j, i, .controlled by said slide valve. The port la, is connected by a duct with the port m, discharging into the rear end of the cylinder at the high .pressure side of the piston. The central port j, re-

ceives the exhaust from the high pressure end of the cylinder and discharges the same into a duct discharging through port l, into the front or low pressure end of the cylinder to throw the piston back to the highV pressure end of the cylinder. The port i, is the exhaust portand receives the exhaust fromv the low pressure ,end of the cylinder through port j, and discharging the exhaust through pipe p, which conveys it to any point desired. The slide valve is provided withv the recess or duct h, in its inner face arranged to register with said ports 'and to place them in communication in the proper order. The ports are all preferably of the same length, and the ports j, and ri,areppreferablyof the same width, but the port k, is of approximately twice the width ofeither one of the other two ports; and the-duct h', in the valve is of such width that when the valve is at its limit of rearward movement and starts forward the rear p vertical edge of the valve will gradually open the port lc, see Fig. 1, and permit live steam from the steam chest toflow into the high pressureend of the cylinder and force the piston forward. While the valve is permitting the live steam to iiow into the high pressure end of the cylinder the duct h, is located over the ports j, t', sothat the steam from the low pressure end of the cylinder is exhausting .through ports l,f 7', t', and the duct h, of the valve. When the valve has exposed one half of the port lo, to thersteam chest, the valve starts on the return strokeV and as it grad ually closes the port lo, to the steam chest the opposite edge of said port lo, is being gradually open to the duct h, of the valve permitting the steam to exhaust from the live steam end of the cylinder through port m, and the inner half of Vport It, duct h, and

kports j, Z, into the low pressure end of the cylinder, and at the same'time the valve breaks communication between port j, and the nal exhaust port. When the valve has IOO exposed one half of its width to the duct h, it starts on the forward stroke. By reason of this peculiar construction and arrange ment it will be observed that the steam is quickly transferred from the high pressure to the low pressure end of the cylinder and that it only has to travel the length of the cylinder so that there is a minimum amount of waste and the engine is operated with great economy of y steam and great power is developed, and the engine is exceedingly quick in action, and but three ports and a single slide valve are employed to accomplish the result desired. It should also be observed that the stroke of the valve will be very short even in a very large engine, and that the exhaust through the passage iu the slide valve forces the same out so thatthe friction of the valve on its seat is reduced to a minimum. Furthermore the weight ot' the valve is comparatively low, therefore the force consumed in operating the valve is reduced to a minimum.

This is a saving of great importance in operating engines.

Having thus fully described my invention, what I claim as new, and desire to secure by Letters Patent of the United States, is-

The cylinder of a compound engine having its valve seat provided at the live steam end with a high pressure port largerin area than the low pressure port, in combination with a slide valve arranged to partially extend over said large port when taking live steam and to close the port to live steam while the steam is passing through it from the high pressure to the low pressure end of the cylinder, substantially as described.

In testimony that I claim the foregoing asv my own I aix my signature in presence of two witnesses.

- H. M. MCCALL.

Witnesses:

HERBERT E. PECK, LEO J. LALLY. 

